How to excite TM10 waves in a waveguide

[htg]

I want to use either a short dipole or a halfwave dipole to excite 150 MHz TM10 waves in a rectangular waveguide. How should I place the dipole and what minimum dimensions of the waveguide should I use?

 

[Chinaski]

Assuming a cutoff freq of 150 MHz and a normalized waveguide (a=2b), you need a 1m x 0.5m waveguide for a TE10 mode (a bit large) Are you sure you want to use a waveguide for this freq?
In a rectangular waveguide neither m nor m subindex can be 0 for TMmn modes

 

[htg]

Yes, I want to use a waveguide. I may go a little up with the frequency (200 MHz). So what if I want TM11 mode?

 

[Chinaski]

I don't get the point. Why do you want to use a TM mode? In rectangular waveguides TE10 or TE01 are always the dominant modes and you are surely going to excite them before a TM mode appears...

 

[htg]

I would like the H field to be perpendicular to the axis of the waveguide. But if this is a problem, then I would like to know the direction of the H field in the TE10 mode.

 

[Chinaski]

Back to the basics...
David M. Pozar, "Microwave Engineering", Ed. John Wiley & Sons, Chapter three

 

[htg]

I do not have the book you mention. I have "Introduction to Electrodynamics" by David J. Griffiths. He doesn't make it clear if the wave in the TE10 mode really moves at an angle to the axis of the waveguide.
My question regarding direction of the H field in the TE10 mode actually refers to a standing wave (i.e. a wave that is standing in the longitudinal direction). What will this direction of H be? I would be thankful for the answer.

 

[asgant]

Re: How to excite TM10 waves in a circular waveguide

I want to model rectangular (TE10) to circular (TM01) mode converter.circular waveguide is perpendicular to rectangular waveguide becoz of field patterns..but how to get the position and dimensions of circular waveguide..can anyone guide me ..

 

[biff44]

since TM10 does not propagate in a normal metallic rectangular waveguide, as others above said, you will have a hard time launching one. Scope this out:
**broken link removed**

 

[FvM]

since TM10 does not propagate in a normal metallic rectangular waveguide

The confusion is caused by intruding the present thread with a different subject. The new question is about rectangular (TE10) to circular (TM01) transition, a standard in radar antenna design.

You'll find a detailed discussion in the Radiation Laboratory Series, Volume 9 Microwave Transmission Circuits, p 379ff, Transitions involving a change in waveguide mode. Downloadable from various internet sources, e.g.

 

[biff44]

so exactly what mode to what mode IS wanted?

 

[asgant]

Till now i'"m not clear about these mode transistions..

 

[FvM]

Why? The principle geometry is given in literature, also hints about avoidance of unwanted modes. As long as you don't find a ready-to-use construction manual, you'll need to work out the details yourself, using an EM solver.

 

[asgant]

Hii biff44..
I want to excite TM01 mode in circular waveguide..Can u tell me how to do in Ansoft HFSS..Should i increase the no .of modes in waveport excitation so that whatever mode i want i can excite by assigning 1 in e-field sources..
Or else will that depends on frequency and diameter of the waveguide..
Is this clear..

 

[davenn]

asgant

you have caused confusion in this thread because you have posted your question in some one elses thread
you should have started your own thread

Moderators, can you please move asgant's posts to his own thread to save on continuing confusion

Dave